A full resistance zero point compensation method for six-dimensional force sensor

Abstract

The present invention discloses a method for full resistance zero-point compensation of a six-dimensional force sensor. The method comprises: forming a Wheatstone bridge corresponding to each measurement dimension of the six-dimensional force sensor, wherein the Wheatstone bridge further comprises a bridge switching circuit; controlling the connection between each single-pole double-throw switch in the Wheatstone bridge requiring zero-point compensation and the bridge switching circuit, changing the Wheatstone bridge assembly mode, and sequentially obtaining a first output voltage, a second output voltage, a third output voltage, and a fourth output voltage; obtaining the initial resistance values ​​of four strain gauges corresponding to the Wheatstone bridge according to the first input voltage, the first output voltage, the second output voltage, the third output voltage, and the fourth output voltage; and welding the short-circuit solder joints of the corresponding strain gauges according to the initial resistance values ​​of the four strain gauges so that the resistance difference between the strain gauges does not exceed a first difference threshold. The zero-point compensation of the present invention can reduce inter-dimensional coupling and improve measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the field of six-dimensional force sensors, and in particular to a full resistance zero point compensation method for six-dimensional force sensors. Background Art

[0002] A multi-dimensional force sensor is a force sensor that can simultaneously measure force and torque components in more than two directions. In a Cartesian coordinate system, force and torque can each be decomposed into three components. Therefore, the most complete form of multi-dimensional force is a six-dimensional force / torque sensor, that is, a sensor that can simultaneously measure three force components and three torque components. This is the most widely used multi-dimensional force sensor. Because six-dimensional force sensors can simultaneously detect three-dimensional forces and three-dimensional torques in space, they can serve as basic components for precision assembly, precision operation, precision control, and human-machine interaction. At the same time, six-dimensional force sensors also ensure that robots can complete contact operations. For example, space exploration technology, space manipulator force control, industrial robots, and remote control of underwater robots all require large-scale, high-precision six-dimensional force sensors.

[0003] Traditional one-dimensional force sensors achieve zero-point compensation by adding compensation resistors to the Wheatstone bridge circuit to rebalance the bridge when unloaded, thus improving force measurement accuracy. However, six-dimensional force sensors must account for the coupling effects between the various dimensions. Adding compensation resistors can increase this coupling, causing the measured data from each dimension to influence each other and reduce accuracy. Summary of the Invention

[0004] In view of some of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a full resistance zero-point compensation method for a six-dimensional force sensor, aiming to perform corresponding compensation on each strain gauge in the Wheatstone bridge to reduce inter-dimensional coupling and improve measurement accuracy.

[0005] To achieve the above object, the present invention provides a method for full resistance zero point compensation of a six-dimensional force sensor, the method comprising:

[0006] Step S1, assembling a Wheatstone bridge corresponding to each measurement dimension of the six-dimensional force sensor; wherein the six-dimensional force sensor further includes a plurality of bridge switching circuits corresponding to the Wheatstone bridges, the bridge switching circuit including two input ends and two output ends, each of the Wheatstone bridges including a first endpoint, a second endpoint, a third endpoint, and a fourth endpoint, and the four endpoints are all connected to a single-pole double-throw switch, and the single-pole double-throw switch is used to switch the connection relationship between the input end and the output end of the bridge switching circuit corresponding to the endpoint;

[0007] Step S2: Controlling each of the single-pole double-throw switches in the Wheatstone bridge requiring zero-point compensation so that the first and third endpoints located at opposite corners are respectively connected to the two input terminals of the bridge switching circuit, and the second and fourth endpoints located at opposite corners are respectively connected to the two output terminals of the bridge switching circuit; applying a positive and a negative first input voltage in sequence between the two input terminals, and measuring at the two output terminals to obtain corresponding first and second output voltages;

[0008] Step S3, controlling each of the single-pole double-throw switches in the Wheatstone bridge requiring zero-point compensation so that the first and third diagonally located endpoints are respectively connected to the two output terminals of the bridge switching circuit, and the second and fourth diagonally located endpoints are respectively connected to the two input terminals of the bridge switching circuit; applying the positive and negative first input voltages sequentially between the two input terminals, and measuring corresponding third and fourth output voltages at the two output terminals;

[0009] Step S4: Obtaining initial resistance values ​​of four strain gauges corresponding to the Wheatstone bridge according to the first input voltage, the first output voltage, the second output voltage, the third output voltage, and the fourth output voltage; wherein some bars of the strain gauge are provided with short-circuit solder joints;

[0010] Step S5: According to the initial resistance values ​​of the four strain gauges, the short-circuit welding points corresponding to the strain gauges are connected by electric welding so that the resistance difference between the strain gauges does not exceed a first difference threshold.

[0011] Optionally, in step S2, the first output voltage and the second output voltage satisfy:

[0012]

[0013]

[0014] in, is the first output voltage, is the second output voltage, is the first input voltage, 、 、 and are the four strain gauges of the Wheatstone bridge, and located between the first endpoint and the second endpoint, located between the second endpoint and the third endpoint, is located between the third endpoint and the fourth endpoint, Located between the fourth endpoint and the first endpoint.

[0015] Optionally, in step S3, the third output voltage and the fourth output voltage satisfy:

[0016]

[0017]

[0018] in, is the third output voltage, is the fourth output voltage, is the first input voltage, 、 、 and are the four strain gauges of the Wheatstone bridge, and located between the first endpoint and the second endpoint, is located between the second endpoint and the third endpoint, is located between the third endpoint and the fourth endpoint, Located between the fourth endpoint and the first endpoint.

[0019] Optionally, step S4 includes:

[0020] according to

[0021]

[0022]

[0023]

[0024]

[0025] Solution 、 、 and .

[0026] Optionally, step S5 includes:

[0027] Obtaining the minimum initial resistance value according to the initial resistance values ​​of the four strain gauges;

[0028] According to the minimum initial resistance, the short-circuit welding points of the strain gauges other than the strain gauge corresponding to the minimum initial resistance are connected by electric welding, so that the resistance difference between the resistance of the other strain gauges and the minimum initial resistance does not exceed a first difference threshold.

[0029] Optionally, after step S5, the method further includes:

[0030] Reapply the test input voltage to the first endpoint and the third endpoint, and obtain the corresponding test output voltage; determine whether the test output voltage is less than the first test threshold, if so, determine that the zero point compensation is completed, otherwise re-compensation is performed.

[0031] Optionally, the strain gauge is connected to the corresponding short-circuit welding point by electric welding to shield part of the grid resistance, thereby reducing the resistance of the strain gauge.

[0032] Optionally, after step S5, the method further includes:

[0033] Repeat steps S2 to S5 for the Wheatstone bridge corresponding to each measurement dimension to complete the full resistance zero point compensation of all the Wheatstone bridges.

[0034] Beneficial effects of the present invention: 1. The present invention changes the input and output of the corresponding Wheatstone bridge through the structure by setting a bridge switching circuit and a single-pole double-throw switch, thereby obtaining different outputs. According to these outputs, the resistance value corresponding to each strain gauge can be solved, and then the full resistance zero-point compensation of each strain gauge can be performed. On the one hand, in this way, the present invention achieves precise compensation. Since it is full resistance compensation, it can avoid the inter-dimensional coupling effect that may be caused by adding only one compensation resistor in the prior art; on the other hand, the present invention can accurately obtain the strain gauge resistance for corresponding compensation without adding other equipment through such a structure, avoiding redundancy, achieving simplification, and making it easier to streamline. 2. Some of the bars of the strain gauge of the present invention are provided with short-circuit solder joints. According to the initial resistance values ​​of the four strain gauges, the present invention connects the short-circuit solder joints of the corresponding strain gauges by electric welding, so that the resistance difference between each strain gauge does not exceed the first difference threshold. Compared with the existing method of adding compensation resistors for zero-point compensation, the present invention does not introduce new compensation resistors, and achieves zero-point compensation by adjusting the resistance of the strain gauge itself, avoiding the situation where the strain gauge resistance changes but the bridge balance is still maintained in the Wheatstone bridge due to the compensation resistor not changing with the deformation or the change amplitude being different from that of the strain gauge, thereby reducing inter-dimensional coupling, increasing the accuracy of zero-point compensation, and improving the accuracy of subsequent force measurement.

[0035] In summary, the present invention can perform corresponding compensation on each strain gauge in the Wheatstone bridge to reduce the inter-dimensional coupling caused by conventional zero-point compensation and improve measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of a method for full resistance zero point compensation of a six-dimensional force sensor provided by a specific embodiment of the present invention;

[0037] Figure 2 1 is a schematic diagram of a circuit structure of a Wheatstone bridge provided by a specific embodiment of the present invention;

[0038] Figure 3 1 is a schematic diagram of an equivalent circuit structure of a Wheatstone bridge corresponding to a first voltage output provided by a specific embodiment of the present invention;

[0039] Figure 4 1 is a schematic diagram of an equivalent circuit structure of a Wheatstone bridge corresponding to a second voltage output provided by a specific embodiment of the present invention;

[0040] Figure 5 1 is a schematic diagram of an equivalent circuit structure of a Wheatstone bridge corresponding to a third voltage output provided by a specific embodiment of the present invention;

[0041] Figure 6 1 is a schematic diagram of an equivalent circuit structure of a Wheatstone bridge corresponding to a fourth voltage output provided by a specific embodiment of the present invention;

[0042] Figure 7 It is a structural schematic diagram of a strain gauge provided by a specific embodiment of the present invention with short-circuit welding points set on the bars. DETAILED DESCRIPTION

[0043] The present invention discloses a method for full resistance zero point compensation of a six-axis force sensor. Those skilled in the art can refer to the content of this article and appropriately improve the technical details. It should be noted in particular that all similar replacements and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments. Relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0044] The applicant's research has found that traditional one-dimensional force sensors achieve zero-point compensation by adding compensation resistors to the Wheatstone bridge circuit to rebalance the bridge when unloaded, resulting in more accurate force measurements. However, six-dimensional force sensors must account for the coupling effects between the various dimensions. Adding compensation resistors can exacerbate these effects, potentially causing the measurement data from each dimension to influence each other and reduce accuracy.

[0045] Therefore, the embodiment of the present invention provides a six-dimensional force sensor full resistance zero compensation method, such as Figure 1 As shown, the method includes:

[0046] Step S1: assembling a Wheatstone bridge corresponding to each measurement dimension of the six-dimensional force sensor.

[0047] Among them, the six-dimensional force sensor also includes multiple bridge switching circuits corresponding to the Wheatstone bridge. The bridge switching circuit includes two input ends and two output ends. Each Wheatstone bridge includes a first endpoint, a second endpoint, a third endpoint and a fourth endpoint, and the four endpoints are all connected to a single-pole double-throw switch. The single-pole double-throw switch is used to switch the connection relationship between the corresponding endpoints between the input end and the output end of the bridge switching circuit.

[0048] Step S2: Control each single-pole double-throw switch in the Wheatstone bridge requiring zero-point compensation so that the first and third endpoints located at opposite corners are respectively connected to the two input terminals of the bridge switching circuit, and the second and fourth endpoints located at opposite corners are respectively connected to the two output terminals of the bridge switching circuit; and apply a positive and negative first input voltage in sequence between the two input terminals, and measure the corresponding first output voltage and second output voltage at the two output terminals.

[0049] It should be noted that a single-pole, double-throw switch can be used to switch the input and output of the Wheatstone bridge, thereby changing its bridge configuration. With the same input voltage (which can be positive or negative), different output voltages can be obtained, which can be used to determine the resistance of each strain gauge. This allows accurate strain gauge resistance to be obtained and compensation to be performed without the need for additional instruments.

[0050] Step S3: Control each single-pole double-throw switch in the Wheatstone bridge requiring zero-point compensation so that the first and third endpoints located at opposite corners are respectively connected to the two output terminals of the bridge switching circuit, and the second and fourth endpoints located at opposite corners are respectively connected to the two input terminals of the bridge switching circuit; and apply a positive and negative first input voltage in sequence between the two input terminals, and measure at the two output terminals to obtain corresponding third and fourth output voltages.

[0051] Step S4: Obtain initial resistance values ​​of four strain gauges corresponding to the Wheatstone bridge according to the first input voltage, the first output voltage, the second output voltage, the third output voltage, and the fourth output voltage, wherein some bars of the strain gauge are provided with short-circuit solder joints.

[0052] In this specific embodiment, the Wheatstone bridge can be Figure 2 As shown, the bridge switching circuit includes two input terminals 201 and 202 and two output terminals 203 and 204. The Wheatstone bridge includes a first terminal 205, a second terminal 206, a third terminal 207 and fourth terminals 208 and 209 which are single-pole double-throw switches.

[0053] In this specific embodiment, the equivalent circuit structure diagram of the Wheatstone bridge corresponding to the first voltage output in step S2 is as follows: Figure 3 As shown, the equivalent circuit structure diagram of the Wheatstone bridge corresponding to the second voltage output in step S2 is as follows Figure 4 As shown, in step S2, the first output voltage and the second output voltage satisfy,

[0054]

[0055]

[0056] in, is the first output voltage, is the second output voltage, is the first input voltage, 、 、 and are the four strain gauges of the Wheatstone bridge, and is located between the first endpoint and the second endpoint, is located between the second endpoint and the third endpoint, is located between the third endpoint and the fourth endpoint, Located between the fourth endpoint and the first endpoint.

[0057] In this specific embodiment, the equivalent circuit structure diagram of the Wheatstone bridge corresponding to the third voltage output in step S3 is as follows: Figure 5 As shown, the equivalent circuit structure diagram of the Wheatstone bridge corresponding to the second voltage output in step S3 is as follows Figure 6 As shown, in step S3, the third output voltage and the fourth output voltage satisfy,

[0058]

[0059]

[0060] in, is the third output voltage, is the fourth output voltage, is the first input voltage, 、 、 and are the four strain gauges of the Wheatstone bridge, and is located between the first endpoint and the second endpoint, is located between the second endpoint and the third endpoint, is located between the third endpoint and the fourth endpoint, Located between the fourth endpoint and the first endpoint.

[0061] In this specific embodiment, step S4 includes:

[0062] according to

[0063]

[0064]

[0065]

[0066]

[0067] Solution 、 、 and .

[0068] Step S5: According to the initial resistance values ​​of the four strain gauges, short-circuit welding points of the corresponding strain gauges are connected by electric welding so that the resistance difference between the strain gauges does not exceed a first difference threshold.

[0069] In this specific embodiment, step S5 includes:

[0070] According to the initial resistance values ​​of the four strain gauges, the minimum initial resistance value is obtained;

[0071] According to the minimum initial resistance, short-circuit welding points of other strain gauges except the strain gauge corresponding to the minimum initial resistance are connected by electric welding so that the resistance difference between the resistance of the other strain gauges and the minimum initial resistance does not exceed a first difference threshold.

[0072] It should be noted that the embodiment of the present invention performs compensation by reducing the resistance value, and therefore it is necessary to perform zero point compensation based on the minimum initial resistance value.

[0073] In this specific embodiment, the strain gauge is connected to the corresponding short-circuit solder joints by electric welding to shield part of the grid resistance, thereby reducing the resistance of the strain gauge.

[0074] In this specific embodiment, the structural diagram of the strain gauge grid bars with short-circuit welding points is as follows: Figure 7 As shown, Figure 7 701 is the strain gauge, and 702 is the shorting solder joint. Connecting these solder joints shields some of the strain gauge resistance, achieving zero-point compensation. This compensation method also avoids introducing new compensation resistors, which could lead to inter-dimensional coupling.

[0075] In this specific embodiment, after step S5, the method further includes:

[0076] Reapply the test input voltage to the first endpoint and the third endpoint, and obtain the corresponding test output voltage; determine whether the test output voltage is less than the first test threshold, if so, determine that the zero point compensation is completed, otherwise re-compensation is performed.

[0077] It should be noted that testing is one of the factory steps and can effectively improve factory quality.

[0078] In this specific embodiment, after step S5, the method further includes:

[0079] Repeat steps S2 to S5 for the Wheatstone bridges corresponding to each measurement dimension to complete the full resistance zero point compensation of all Wheatstone bridges.

[0080] The embodiment of the present invention provides a bridge switching circuit and a single-pole double-throw switch to change the input and output of the corresponding Wheatstone bridge through this structure, thereby obtaining different outputs. Based on these outputs, the resistance value corresponding to each strain gauge can be solved, and then full resistance zero point compensation can be performed on each strain gauge. On the one hand, through this method, the embodiment of the present invention achieves precise compensation. Since it is full resistance compensation, it can avoid the inter-dimensional coupling effect that may be caused by adding only one compensation resistor in the existing technology. On the other hand, the embodiment of the present invention can accurately obtain the strain gauge resistance for corresponding compensation without adding other equipment through such a structure, avoiding redundancy, achieving simplification, and making it easier to streamline.

[0081] In an embodiment of the present invention, some bars of the strain gauge are provided with short-circuit solder joints. In this embodiment, the short-circuit solder joints of the corresponding strain gauges are connected by electric welding based on the initial resistance values ​​of the four strain gauges, so that the resistance difference between the strain gauges does not exceed a first difference threshold. Compared to the existing method of adding compensation resistors for zero-point compensation, the embodiment of the present invention does not introduce new compensation resistors. Instead, zero-point compensation is achieved by adjusting the resistance of the strain gauge itself. This avoids the situation where the strain gauge resistance changes but the bridge remains balanced in the Wheatstone bridge because the compensation resistor does not change with deformation or the resistance change amplitude differs from that of the strain gauge. This reduces inter-dimensional coupling, increases the accuracy of zero-point compensation, and improves the accuracy of subsequent force measurements.

[0082] In summary, the embodiments of the present invention can perform corresponding compensation on each strain gauge in the Wheatstone bridge to reduce the inter-dimensional coupling caused by conventional zero-point compensation and improve measurement accuracy.

[0083] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0084] Each embodiment in this specification is described in a related manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiment is generally similar to the method embodiment, so the description is relatively simple. For related parts, refer to the description of the method embodiment.

[0085] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A six-dimensional force sensor full resistance zero point compensation method, characterized in that: The method comprises: Step S1, assembling a Wheatstone bridge corresponding to each measurement dimension of the six-dimensional force sensor; wherein the six-dimensional force sensor further includes a plurality of bridge switching circuits corresponding to the Wheatstone bridges, the bridge switching circuit including two input ends and two output ends, each of the Wheatstone bridges including a first endpoint, a second endpoint, a third endpoint, and a fourth endpoint, and the four endpoints are all connected to a single-pole double-throw switch, and the single-pole double-throw switch is used to switch the connection relationship between the input end and the output end of the bridge switching circuit corresponding to the endpoint; Step S2: Controlling each of the single-pole double-throw switches in the Wheatstone bridge requiring zero-point compensation so that the first and third endpoints located at opposite corners are respectively connected to the two input terminals of the bridge switching circuit, and the second and fourth endpoints located at opposite corners are respectively connected to the two output terminals of the bridge switching circuit; applying a positive and a negative first input voltage in sequence between the two input terminals, and measuring at the two output terminals to obtain corresponding first and second output voltages; Step S3, controlling each of the single-pole double-throw switches in the Wheatstone bridge requiring zero-point compensation so that the first and third diagonally located endpoints are respectively connected to the two output terminals of the bridge switching circuit, and the second and fourth diagonally located endpoints are respectively connected to the two input terminals of the bridge switching circuit; applying the positive and negative first input voltages sequentially between the two input terminals, and measuring corresponding third and fourth output voltages at the two output terminals; Step S4: Obtaining initial resistance values ​​of four strain gauges corresponding to the Wheatstone bridge according to the first input voltage, the first output voltage, the second output voltage, the third output voltage, and the fourth output voltage; wherein some bars of the strain gauge are provided with short-circuit solder joints; Step S5: According to the initial resistance values ​​of the four strain gauges, the short-circuit welding points corresponding to the strain gauges are connected by electric welding so that the resistance difference between the strain gauges does not exceed a first difference threshold.

2. The six-dimensional force sensor full resistance zero compensation method according to claim 1, characterized in that: In step S2, the first output voltage and the second output voltage satisfy: in, is the first output voltage, is the second output voltage, is the first input voltage, 、 、 and are the four strain gauges of the Wheatstone bridge, and located between the first endpoint and the second endpoint, is located between the second endpoint and the third endpoint, is located between the third endpoint and the fourth endpoint, Located between the fourth endpoint and the first endpoint.

3. The six-dimensional force sensor full resistance zero compensation method according to claim 2, characterized in that: In step S3, the third output voltage and the fourth output voltage satisfy: in, is the third output voltage, is the fourth output voltage, is the first input voltage, 、 、 and are the four strain gauges of the Wheatstone bridge, and located between the first endpoint and the second endpoint, is located between the second endpoint and the third endpoint, is located between the third endpoint and the fourth endpoint, Located between the fourth endpoint and the first endpoint.

4. The six-dimensional force sensor full resistance zero compensation method according to claim 3, characterized in that: The step S4 comprises: according to Solution 、 、 and .

5. The six-dimensional force sensor full resistance zero compensation method according to claim 1, characterized in that: The step S5 comprises: Obtaining the minimum initial resistance value according to the initial resistance values ​​of the four strain gauges; According to the minimum initial resistance, the short-circuit welding points of the strain gauges other than the strain gauge corresponding to the minimum initial resistance are connected by electric welding, so that the resistance difference between the resistance of the other strain gauges and the minimum initial resistance does not exceed a first difference threshold.

6. The six-dimensional force sensor full resistance zero compensation method according to claim 1, characterized in that: After step S5, the method further includes: Reapply the test input voltage to the first endpoint and the third endpoint, and obtain the corresponding test output voltage; determine whether the test output voltage is less than the first test threshold, if so, determine that the zero point compensation is completed, otherwise re-compensation is performed.

7. The six-dimensional force sensor full resistance zero compensation method according to claim 1, characterized in that: The strain gauge is connected to the corresponding short-circuit welding point by electric welding to shield part of the grid resistance, thereby reducing the resistance of the strain gauge.

8. The six-dimensional force sensor full resistance zero compensation method according to claim 1, characterized in that: After step S5, the method further includes: Repeat steps S2 to S5 for the Wheatstone bridge corresponding to each measurement dimension to complete the full resistance zero point compensation of all the Wheatstone bridges.

Images